Resolves "Generalize NTCSensor"

• The NTCSensor class now takes an ADCDevice instead of TextSerialCom as an input. Resolves issue #63
• Supports different voltage divider wiring options: choose between read voltage drop over NTC or over divider resistor with readoverntc=true.
• Steinhart-Hart temperature conversion can be activated with steinhart=true which is more accurate over a wider range than using the beta formula.